Substrate effects on the epitaxial growth of AlN thin films using electron cyclotron resonance plasma enhanced chemical vapor deposition

Abstract

Highly c-axis oriented AlN films were fabricated on various substrates by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) at a substrate temperature of 500 degrees C. The degree of c-axis orientation depends sensitively on the substrate: the standard deviations sigma of AlN(0002) rocking curve peaks are 4.9 degrees, 4.8 degrees, 4.3 degrees, 4.0 degrees and 1.5 degrees on SiO2, Si3N4, Si(100), Si(111) and alpha-Al2O3(0001) substrates, respectively The amorphous interfacial silicon oxide layer on Si substrate has an important effect on the degree of c-axis orientation and in-plane alignment of the AlN film. The AlN films prepared by ECR PECVD have much lower surface roughness (R(RMS) = 1.1-1.9 nm) than the sputter-deposited films (R(RMS) = 3.0-9.0 nm), which offers lower propagation loss in SAW devices.